This invention relates to the general field of turbogenerator controls, and more particularly to an improved method and system for automatically restarting the turbogenerator under certain fault conditions.
A turbogenerator with a shaft mounted permanent magnet motor/generator can be utilized to provide electrical power for a wide range of utility, commercial and industrial applications. While an individual permanent magnet turbogenerator may only generate 20 to 100 kilowatts, powerplants of up to 500 kilowatts or greater are possible by linking numerous permanent magnet turbogenerators together. Peak load shaving power, grid parallel power, standby power, and remote location (standalone) power are just some of the potential applications for which these lightweight, low noise, low cost, environmentally friendly, and thermally efficient units can be useful.
The conventional power control system for a turbogenerator produces constant frequency, three phase electrical power that closely approximates the electrical power produced by utility grids. Key aspects of such a power generation system are availability and reliability.
In grid-connect power generation, lack of availability can result in penalties from the local utility. Since many utility users are charged variable rates depending upon the amount of power drawn during a given period of time, the lowest $/kWh is charged when power is drawn at levels lower than some negotiated base. Power drawn above the base level will usually have greatly increased fees and sometimes a penalty associated with it. While grid-connect power generation can be used to provide less expensive power when more than the utility base level of power is required, should this grid-connect power generation fail, or otherwise be unavailable, greater costs to the user would ensue.
Availability and reliability are even more important in a standalone system in which the turbogenerator itself is providing the entire load for a user. If the turbogenerator is unavailable, lengthy interruptions to all aspects of a user""s business can occur and result in significant financial loss to the user. For remote installations, the turbogenerator could be down for a lengthy period of time since it might take a while for a service person to provide support at the remote site.
The invention is directed to a method and system to automatically restart a permanent magnet turbogenerator/motor when a fatal fault is detected. The automatic restart logic includes time constraints and limitations on the number of iterations. If successful, the automatic restarting of the permanent magnet turbogenerator/motor eliminates the costly need for a complete shutdown. The automatic restart is useful regardless of whether the permanent magnet turbogenerator/motor is in a grid connect mode or a standalone mode, and regardless of how the fatal fault originates or is detected. Additional control logic is utilized to handle grid transients and over load conditions to prevent a fatal fault from occurring by using time constraints and an iterative process, together with a brake resistor to control DC bus voltage.